document_title: Gas metal arc welding

question_text: what is the function of wire feeder in mig mag welding

text: Gas metal arc welding

text: Development[edit]

text: The principles of gas metal arc welding began to be understood in the early 19th century, after Humphry Davy discovered the short pulsed electric arcs in 1800.[1] Vasily Petrov independently produced the continuous electric arc in 1802 (followed by Davy after 1808).[1] It was not until the 1880s that the technology became developed with the aim of industrial usage. At first, carbon electrodes were used in carbon arc welding. By 1890, metal electrodes had been invented by Nikolay Slavyanov and C. L. Coffin. In 1920, an early predecessor of GMAW was invented by P. O. Nobel of General Electric. It used direct current with a bare electrode wire and used arc voltage to regulate the feed rate. It did not use a shielding gas to protect the weld, as developments in welding atmospheres did not take place until later that decade. In 1926 another forerunner of GMAW was released, but it was not suitable for practical use.[2]

text: In 1948, GMAW was developed by the Battelle Memorial Institute. It used a smaller diameter electrode and a constant voltage power source developed by H. E. Kennedy. It offered a high deposition rate, but the high cost of inert gases limited its use to non-ferrous materials and prevented cost savings. In 1953, the use of carbon dioxide as a welding atmosphere was developed, and it quickly gained popularity in GMAW, since it made welding steel more economical. In 1958 and 1959, the short-arc variation of GMAW was released, which increased welding versatility and made the welding of thin materials possible while relying on smaller electrode wires and more advanced power supplies. It quickly became the most popular GMAW variation.

text: The spray-arc transfer variation was developed in the early 1960s, when experimenters added small amounts of oxygen to inert gases. More recently, pulsed current has been applied, giving rise to a new method called the pulsed spray-arc variation.[3]

text: GMAW is one of the most popular welding methods, especially in industrial environments.[4] It is used extensively by the sheet metal industry and the automobile industry. There, the method is often used for arc spot welding, replacing riveting or resistance spot welding. It is also popular for automated welding, where robots handle the workpieces and the welding gun to accelerate manufacturing.[5] GMAW can be difficult to perform well outdoors, since drafts can dissipate the shielding gas and allow contaminants into the weld;[6] flux cored arc welding is better suited for outdoor use such as in construction.[7][8] Likewise, GMAW's use of a shielding gas does not lend itself to underwater welding, which is more commonly performed via shielded metal arc welding, flux cored arc welding, or gas tungsten arc welding.[9]

text: Equipment[edit]

text: To perform gas metal arc welding, the basic necessary equipment is a welding gun, a wire feed unit, a welding power supply, a welding electrode wire, and a shielding gas supply.[10]

text: Welding gun and wire feed unit[edit]

text: The typical GMAW welding gun has a number of key parts—a control switch, a contact tip, a power cable, a gas nozzle, an electrode conduit and liner, and a gas hose. The control switch, or trigger, when pressed by the operator, initiates the wire feed, electric power, and the shielding gas flow, causing an electric arc to be struck. The contact tip, normally made of copper and sometimes chemically treated to reduce spatter, is connected to the welding power source through the power cable and transmits the electrical energy to the electrode while directing it to the weld area.  It must be firmly secured and properly sized, since it must allow the electrode to pass while maintaining electrical contact. On the way to the contact tip, the wire is protected and guided by the electrode conduit and liner, which help prevent buckling and maintain an uninterrupted wire feed. The gas nozzle directs the shielding gas evenly into the welding zone. Inconsistent flow may not adequately protect the weld area. Larger nozzles provide greater shielding gas flow, which is useful for high current welding operations that develop a larger molten weld pool.  A gas hose from the tanks of shielding gas supplies the gas to the nozzle. Sometimes, a water hose is also built into the welding gun, cooling the gun in high heat operations.[11]

text: The wire feed unit supplies the electrode to the work, driving it through the conduit and on to the contact tip.  Most models provide the wire at a constant feed rate, but more advanced machines can vary the feed rate in response to the arc length and voltage.  Some wire feeders can reach feed rates as high as 30.5 m/min (1200 in/min),[12] but feed rates for semiautomatic GMAW typically range from 2 to 10 m/min (75 – 400 in/min).[13]

text: Tool style[edit]

text: The most common electrode holder is a semiautomatic air-cooled holder. Compressed air circulates through it to maintain moderate temperatures. It is used with lower current levels for welding lap or butt joints. The second most common type of electrode holder is semiautomatic water-cooled, where the only difference is that water takes the place of air. It uses higher current levels for welding T or corner joints. The third typical holder type is a water cooled automatic electrode holder—which is typically used with automated equipment.[14]

text: Power supply[edit]

text: Most applications of gas metal arc welding use a constant voltage power supply.  As a result, any change in arc length (which is directly related to voltage) results in a large change in heat input and current. A shorter arc length causes a much greater heat input, which makes the wire electrode melt more quickly and thereby restore the original arc length. This helps operators keep the arc length consistent even when manually welding with hand-held welding guns. To achieve a similar effect, sometimes a constant current power source is used in combination with an arc voltage-controlled wire feed unit.  In this case, a change in arc length makes the wire feed rate adjust to maintain a relatively constant arc length. In rare circumstances, a constant current power source and a constant wire feed rate unit might be coupled, especially for the welding of metals with high thermal conductivities, such as aluminum.  This grants the operator additional control over the heat input into the weld, but requires significant skill to perform successfully.[15]

text: Alternating current is rarely used with GMAW; instead, direct current is employed and the electrode is generally positively charged.  Since the anode tends to have a greater heat concentration, this results in faster melting of the feed wire, which increases weld penetration and welding speed.  The polarity can be reversed only when special emissive-coated electrode wires are used, but since these are not popular, a negatively charged electrode is rarely employed.[16]

text: Electrode[edit]

text: Electrode selection is based primarily on the composition of the metal being welded, the process variation being used, joint design and the material surface conditions. Electrode selection greatly influences the mechanical properties of the weld and is a key factor of weld quality. In general the finished weld metal should have mechanical properties similar to those of the base material with no defects such as discontinuities, entrained contaminants or porosity within the weld. To achieve these goals a wide variety of electrodes exist.  All commercially available electrodes contain deoxidizing metals such as silicon, manganese, titanium and aluminum in small percentages to help prevent oxygen porosity. Some contain denitriding metals such as titanium and zirconium to avoid nitrogen porosity.[17] Depending on the process variation and base material being welded the diameters of the electrodes used in GMAW typically range from 0.7 to 2.4 mm (0.028 – 0.095 in) but can be as large as 4 mm (0.16 in). The smallest electrodes, generally up to 1.14 mm (0.045 in)[18] are associated with the short-circuiting metal transfer process, while the most common spray-transfer process mode electrodes are usually at least 0.9 mm (0.035 in).[19][20]

text: Shielding gas[edit]

text: Shielding gases are necessary for gas metal arc welding to protect the welding area from atmospheric gases such as nitrogen's and oxygen, which can cause fusion defects, porosity, and weld metal embrittlement if they come in contact with the electrode, the arc, or the welding metal. This problem is common to all arc welding processes; for example, in the older Shielded-Metal Arc Welding process (SMAW), the electrode is coated with a solid flux which evolves a protective cloud of carbon dioxide when melted by the arc. In GMAW, however, the electrode wire does not have a flux coating, and a separate shielding gas is employed to protect the weld. This eliminates slag, the hard residue from the flux that builds up after welding and must be chipped off to reveal the completed weld.[21]

text: The choice of a shielding gas depends on several factors, most importantly the type of material being welded and the process variation being used. Pure inert gases such as argon and helium are only used for nonferrous welding; with steel they do not provide adequate weld penetration (argon) or cause an erratic arc and encourage spatter (with helium). Pure carbon dioxide, on the other hand, allows for deep penetration welds but encourages oxide formation, which adversely affects the mechanical properties of the weld. lts low cost makes it an attractive choice, but because of the reactivity of the arc plasma, spatter is unavoidable and welding thin materials is difficult. As a result, argon and carbon dioxide are frequently mixed in a 75%/25% to 90%/10% mixture. Generally, in short circuit GMAW, higher carbon dioxide content increases the weld heat and energy when all other weld parameters (volts, current, electrode type and diameter) are held the same. As the carbon dioxide content increases over 20%, spray transfer GMAW becomes increasingly problematic, especially with smaller electrode diameters.[22]

text: Argon is also commonly mixed with other gases, oxygen, helium, hydrogen and nitrogen. The addition of up to 5% oxygen (like the higher concentrations of carbon dioxide mentioned above) can be helpful in welding stainless steel, however, in most applications carbon dioxide is preferred.[23] Increased oxygen makes the shielding gas oxidize the electrode, which can lead to porosity in the deposit if the electrode does not contain sufficient deoxidizers. Excessive oxygen, especially when used in application for which it is not prescribed, can lead to brittleness in the heat affected zone. Argon-helium mixtures are extremely inert, and can be used on nonferrous materials. A helium concentration of 50–75% raises the required voltage and increases the heat in the arc, due to helium's higher ionization temperature. Hydrogen is sometimes added to argon in small concentrations (up to about 5%) for welding nickel and thick stainless steel workpieces. In higher concentrations (up to 25% hydrogen), it may be used for welding conductive materials such as copper. However, it should not be used on steel, aluminum or magnesium because it can cause porosity and hydrogen embrittlement.[21]

text: Shielding gas mixtures of three or more gases are also available. Mixtures of argon, carbon dioxide and oxygen are marketed for welding steels. Other mixtures add a small amount of helium to argon-oxygen combinations, these mixtures are claimed to allow higher arc voltages and welding speed. Helium also sometimes serves as the base gas, with small amounts of argon and carbon dioxide added. However, because it is less dense than air, helium is less effective at shielding the weld than argon—which is denser than air. It also can lead to arc stability and penetration issues, and increased spatter, due to its much more energetic arc plasma. Helium is also substantially more expensive than other shielding gases. Other specialized and often proprietary gas mixtures claim even greater benefits for specific applications.[21]

text: The desirable rate of shielding-gas flow depends primarily on weld geometry, speed, current, the type of gas, and the metal transfer mode. Welding flat surfaces requires higher flow than welding grooved materials, since gas disperses more quickly. Faster welding speeds, in general, mean that more gas must be supplied to provide adequate coverage. Additionally, higher current requires greater flow, and generally, more helium is required to provide adequate coverage than if argon is used. Perhaps most importantly, the four primary variations of GMAW have differing shielding gas flow requirements—for the small weld pools of the short circuiting and pulsed spray modes, about 10 L/min (20 ft³/h) is generally suitable, whereas for globular transfer, around 15 L/min (30 ft³/h) is preferred.  The spray transfer variation normally requires more shielding-gas flow because of its higher heat input and thus larger weld pool. Typical gas-flow amounts are approximately 20–25 L/min (40–50 ft³/h).[13]

text: GMAW-based 3-D printing[edit]

text: GMAW has also been used as a low-cost method to 3-D print metal objects. [24][25][26] Various open source 3-D printers have been developed to use GMAW. [27] Such components fabricated from aluminum compete with more traditionally manufactured components on mechanical strength. [28] By forming a bad weld on the first layer, GMAW 3-D printed parts can be removed from the substrate with a hammer.[29][30]

text: Operation[edit]

text: For most of its applications gas metal arc welding is a fairly simple welding process to learn requiring no more than a week or two to master basic welding technique. Even when welding is performed by well-trained operators weld quality can fluctuate since it depends on a number of external factors. All GMAW is dangerous, though perhaps less so than some other welding methods, such as shielded metal arc welding.[31]

text: Technique[edit]

text: GMAW's basic technique is uncomplicated, with most individuals able to achieve reasonable proficiency in a few weeks, assuming proper training and sufficient practice.   As much of the process is automated, GMAW relieves the weldor (operator)  of the burden of maintaining a precise arc length, as well as feeding filler metal into the weld puddle, coordinated operations that are required in other manual welding processes, such as shielded metal arc.  GMAW requires only that the weldor guide the gun with proper position and orientation along the area being welded, as well as periodically clean the gun's gas nozzle to remove spatter buildup.  Additional skill includes knowing how to adjust the welder so the voltage, wire feed rate and gas flow rate are correct for the materials being welded and the wire size being employed.

text: Maintaining a relatively constant contact tip-to-work distance (the stick-out distance) is important.  Excessive stick-out distance may cause the wire electrode to prematurely melt, causing a sputtering arc, and may also cause the shielding gas to rapidly disperse, degrading the quality of the weld. In contrast, insufficient stick-out may increase the rate at which spatter builds up inside the gun's nozzle and in extreme cases, may cause damage to the gun's contact tip.  Stick-out distance varies for different GMAW weld processes and applications.[32][33][34][35]

text: The orientation of the gun relative to the weldment is also important.  It should be held so as to bisect the angle between the workpieces; that is, at 45 degrees for a fillet weld and 90 degrees for welding a flat surface. The travel angle, or lead angle, is the angle of the gun with respect to the direction of travel, and it should generally remain approximately vertical.[citation needed] However, the desirable angle changes somewhat depending on the type of shielding gas used—with pure inert gases, the bottom of the torch is often slightly in front of the upper section, while the opposite is true when the welding atmosphere is carbon dioxide.[36]

text: Position welding, that is, welding vertical or overhead joints, may require the use of a weaving technique to assure proper weld deposition and penetration.  In position welding, gravity tends to cause molten metal to run out of the puddle, resulting in cratering and undercutting, two conditions that produce a weak weld.  Weaving constantly moves the fusion zone around so as to limit the amount of metal deposited at any one point.  Surface tension then assists in keeping the molten metal in the puddle until it is able to solidify.  Development of position welding skill takes some experience, but is usually soon mastered.

text: Quality[edit]

text: Two of the most prevalent quality problems in GMAW are dross and porosity. If not controlled, they can lead to weaker, less ductile welds. Dross is an especially common problem in aluminium GMAW welds, normally coming from particles of aluminium oxide or aluminum nitride present in the electrode or base materials. Electrodes and workpieces must be brushed with a wire brush or chemically treated to remove oxides on the surface. Any oxygen in contact with the weld pool, whether from the atmosphere or the shielding gas, causes dross as well. As a result, sufficient flow of inert shielding gases is necessary, and welding in moving air should be avoided.[37]

text: In GMAW the primary cause of porosity is gas entrapment in the weld pool, which occurs when the metal solidifies before the gas escapes. The gas can come from impurities in the shielding gas or on the workpiece, as well as from an excessively long or violent arc. Generally, the amount of gas entrapped is directly related to the cooling rate of the weld pool. Because of its higher thermal conductivity, aluminum welds are especially susceptible to greater cooling rates and thus additional porosity. To reduce it, the workpiece and electrode should be clean, the welding speed diminished and the current set high enough to provide sufficient heat input and stable metal transfer but low enough that the arc remains steady. Preheating can also help reduce the cooling rate in some cases by reducing the temperature gradient between the weld area and the base metal.[38]

text: Safety[edit]

text: Arc welding in any form can be dangerous if proper precautions are not taken. Since GMAW employs an electric arc, weldors must wear suitable protective clothing, including heavy gloves and protective long sleeve jackets, to minimize exposure to the arc itself, as well as intense heat, sparks and hot metal. The intense ultraviolet radiation of the arc may cause sunburn-like damage to exposed skin, as well a condition known as arc eye, an inflammation of the cornea, or in cases of prolonged exposure, irreversible damage to the eye's retina. Conventional welding helmets contain dark face plates to prevent this exposure. Newer helmet designs feature a liquid crystal-type face plate that self-darkens upon exposure to the arc. Transparent welding curtains, made of a polyvinyl chloride plastic film, are often used to shield nearby workers and bystanders from exposure to the arc.[39]

text: Weldors are often exposed to hazardous gases and airborne particulate matter. GMAW produces smoke containing particles of various types of oxides, and the size of the particles tends to influence the toxicity of the fumes. Smaller particles present greater danger. Concentrations of carbon dioxide and ozone can prove dangerous if ventilation is inadequate. Other precautions include keeping combustible materials away from the workplace, and having a working fire extinguisher nearby.[40]

text: Metal transfer modes[edit]

text: The three transfer modes in GMAW are globular, short-circuiting, and spray. There are a few recognized variations of these three transfer modes including modified short-circuiting and pulsed-spray.[41]

text: Globular[edit]

text: GMAW with globular metal transfer is considered the least desirable of the three major GMAW variations, because of its tendency to produce high heat, a poor weld surface, and spatter. The method was originally developed as a cost efficient way to weld steel using GMAW, because this variation uses carbon dioxide, a less expensive shielding gas than argon. Adding to its economic advantage was its high deposition rate, allowing welding speeds of up to 110 mm/s (250 in/min).[42] As the weld is made, a ball of molten metal from the electrode tends to build up on the end of the electrode, often in irregular shapes with a larger diameter than the electrode itself. When the droplet finally detaches either by gravity or short circuiting, it falls to the workpiece, leaving an uneven surface and often causing spatter.[43] As a result of the large molten droplet, the process is generally limited to flat and horizontal welding positions, requires thicker workpieces, and results in a larger weld pool.[44][45]

text: Short-circuiting[edit]

text: Further developments in welding steel with GMAW led to a variation known as short-circuit transfer (SCT) or short-arc GMAW, in which the current is lower than for the globular method. As a result of the lower current, the heat input for the short-arc variation is considerably reduced, making it possible to weld thinner materials while decreasing the amount of distortion and residual stress in the weld area. As in globular welding, molten droplets form on the tip of the electrode, but instead of dropping to the weld pool, they bridge the gap between the electrode and the weld pool as a result of the lower wire feed rate.  This causes a short circuit and extinguishes the arc, but it is quickly reignited after the surface tension of the weld pool pulls the molten metal bead off the electrode tip. This process is repeated about 100 times per second, making the arc appear constant to the human eye. This type of metal transfer provides better weld quality and less spatter than the globular variation, and allows for welding in all positions, albeit with slower deposition of weld material. Setting the weld process parameters (volts, amps and wire feed rate) within a relatively narrow band is critical to maintaining a stable arc: generally between 100 and 200 amperes at 17 to 22 volts for most applications. Also, using short-arc transfer can result in lack of fusion and insufficient penetration when welding thicker materials, due to the lower arc energy and rapidly freezing weld pool.[46] Like the globular variation, it can only be used on ferrous metals.[20][47][48]

text: Cold Metal Transfer[edit]

text: For thin materials, Cold Metal Transfer (CMT) is used by reducing the current when a short circuit is registered, producing many drops per second. CMT can be used for aluminum.

text: Spray[edit]

text: Spray transfer GMAW was the first metal transfer method used in GMAW, and well-suited to welding aluminium and stainless steel while employing an inert shielding gas. In this GMAW process, the weld electrode metal is rapidly passed along the stable electric arc from the electrode to the workpiece, essentially eliminating spatter and resulting in a high-quality weld finish. As the current and voltage increases beyond the range of short circuit transfer the weld electrode metal transfer transitions from larger globules through small droplets to a vaporized stream at the highest energies.[49] Since this vaporized spray transfer variation of the GMAW weld process requires higher voltage and current than short circuit transfer, and as a result of the higher heat input and larger weld pool area (for a given weld electrode diameter), it is generally used only on workpieces of thicknesses above about 6.4 mm (0.25 in).[50]

text: Also, because of the large weld pool, it is often limited to flat and horizontal welding positions and sometimes also used for vertical-down welds. It is generally not practical for root pass welds.[51] When a smaller electrode is used in conjunction with lower heat input, its versatility increases.  The maximum deposition rate for spray arc GMAW is relatively high—about 60 mm/s (150 in/min).[20][42][52]

text: Pulsed-spray[edit]

text: A variation of the spray transfer mode, pulse-spray is based on the principles of spray transfer but uses a pulsing current to melt the filler wire and allow one small molten droplet to fall with each pulse. The pulses allow the average current to be lower, decreasing the overall heat input and thereby decreasing the size of the weld pool and heat-affected zone while making it possible to weld thin workpieces. The pulse provides a stable arc and no spatter, since no short-circuiting takes place. This also makes the process suitable for nearly all metals, and thicker electrode wire can be used as well. The smaller weld pool gives the variation greater versatility, making it possible to weld in all positions. In comparison with short arc GMAW, this method has a somewhat slower maximum speed (85 mm/s or 200 in/min) and the process also requires that the shielding gas be primarily argon with a low carbon dioxide concentration. Additionally, it requires a special power source capable of providing current pulses with a frequency between 30 and 400 pulses per second. However, the method has gained popularity, since it requires lower heat input and can be used to weld thin workpieces, as well as nonferrous materials.[20][53][54][55]

text: Comparison with flux-cored wire-fed arc welding[edit]

text: Flux-cored, self-shielding or gasless wire-fed welding had been developed for simplicity and portability.[56] This avoids the gas system of conventional GMAW and uses a cored wire containing a solid flux. This flux vaporises during welding and produces a plume of shielding gas. Although described as a 'flux', this compound has little activity and acts mostly as an inert shield. The wire is of slightly larger diameter than for a comparable gas-shielded weld, to allow room for the flux. The smallest available is 0.8 mm diameter, compared to 0.6 mm for solid wire. The shield vapor is slightly active, rather than inert, so the process is always MAGS but not MIG (inert gas shield). This limits the process to steel and not aluminium.

text: Vaporising the additional flux requires greater heat in the wire, so these gasless machines operate as DCEP, rather than the DCEN usually used for GMAW to give deeper penetration.[56] DCEP, or DC Electrode Positive, makes the welding wire into the positively-charged anode, which is the hotter side of the arc.[57] Provided that it is switchable from DCEN to DCEP, a gas-shielded wire-feed machine may also be used for flux-cored wire.

text: Flux-cored wire is considered to have some advantages for outdoor welding on-site, as the shielding gas plume is less likely to be blown away in a wind than shield gas from a conventional nozzle.[58][59] A slight drawback is that, like SMAW (stick) welding, there may be some flux deposited over the weld bead, requiring more of a cleaning process between passes.[58]

text: Flux-cored welding machines are most popular at the hobbyist level, as the machines are slightly simpler but mainly because they avoid the cost of providing shield gas, either through a rented cylinder or with the high cost of disposable cylinders.[58]


document_title: Alien vs. Predator (film)

question_text: who played the predator in alien vs predator

root

text: Alien vs. Predator (film)

text: Plot[edit]

text: In 2004, a satellite detects a mysterious heat bloom beneath Bouvetøya, an island about one thousand miles off the coast of Antarctica. Wealthy industrialist Charles Bishop Weyland (Lance Henriksen) discovers through thermal imaging that there is a pyramid buried 2000 feet beneath the ice. He attempts to claim it for his multinational communications company, Weyland Industries, a subsidiary of the Weyland Corporation, and assembles a team of experts to investigate. The team includes archaeologists, linguistic experts, drillers, mercenaries, and a guide named Alexa Woods (Sanaa Lathan).

tag: p

text: As a Predator ship reaches Earth's orbit, it fires a beam that creates a passage through the ice towards the source of the heat bloom. When the team arrives at the abandoned whaling station above the heat source, they find the passage and descend beneath the ice. They locate the mysterious pyramid and begin to explore it, finding evidence of a prehistoric civilization and what appears to be a sacrificial chamber filled with human skeletons with ruptured rib cages.

text: Meanwhile, three Predators consisting of Scar, Celtic and Chopper arrive and kill all the humans on the surface. They make their way down to the pyramid and arrive just as the team unwittingly activates the structure. The Alien Queen awakes from cryogenic stasis and begins to produce eggs. When the eggs hatch, several facehuggers attach themselves to humans trapped in the sacrificial chamber. Chestbursters emerge from the humans and quickly grow into adult Aliens. Conflict erupts between the Predators, Aliens, and humans, resulting in several deaths. Celtic and Chopper are killed by an Alien, and Weyland buys Alexa and Italian archaeologist Sebastian De Rosa (Raoul Bova) enough time to escape from Scar, giving his life in the process. The two witness Scar kill a facehugger and an Alien with a shuriken before unmasking and marking himself with the blood of the facehugger. After Alexa and Sebastian leave, another facehugger attaches itself to Scar due to him not wearing his mask.

text: Through translation of the pyramid's hieroglyphs, Alexa and Sebastian learn that the Predators have been visiting Earth for thousands of years. It was they who taught early human civilizations how to build pyramids, and were worshiped as gods. Every 100 years they visited Earth to take part in a rite of passage by which several humans sacrifice themselves as hosts for the Aliens, creating the "ultimate prey" for the Predators to hunt while being able to survive in the pyramid; if overwhelmed, the Predators would activate a self-destruct device to eliminate the Aliens and themselves. The two deduce that this is why the current Predators are at the pyramid, and that the heat bloom was to attract humans for the sole purpose of making new Aliens to hunt.

text: Alexa and Sebastian decide that the Predators must be allowed to succeed in their hunt so that the Aliens "do not reach the surface". Then Sebastian is captured by an Alien, leaving only Alexa and Scar to fight the Aliens. The two form an alliance and use a self-destruct device to destroy the pyramid and the remaining Aliens. Alexa and Scar reach the surface, where they battle the Alien Queen. They defeat the Queen by attaching its chain to a water tower and pushing her over a cliff, dragging the Queen to the ocean floor. Scar, however, is impaled through the torso by the Alien Queen's tail and succumbs to his wounds and dies.

text: A Predator ship uncloaks and several Predators appear. They retrieve their fallen comrade and an elite Predator presents Alexa with one of their spear weapons in recognition of her skill as a warrior symbolized by the alien blood Scar burned on her cheek before he died. As the Predators retreat into space, a chestburster with a hybrid form of an Alien and a Predator erupts from Scar's chest.

text: Cast[edit]

text:
Sanaa Lathan as Alexa Woods, an experienced guide who spent several seasons exploring the Arctic and Antarctic environments.
Lance Henriksen as Charles Bishop Weyland, the billionaire head of Weyland Industries, a subsidiary of the Weyland Corporation, which he is also the head of.
Raoul Bova as Sebastian De Rosa, an Italian archaeologist who is able to translate the pyramid's hieroglyphs.
Ewen Bremner as Graeme Miller, a chemical engineer of the exploration team.
Colin Salmon as Maxwell "Max" Stafford, assistant to Mr. Weyland and former British Special Forces (SAS) Officer.
Tommy Flanagan as Mark Verheiden, a mercenary member of the exploration team.
Joseph Rye as Joe Connors, a member of the exploration team.
Agathe de La Boulaye as Adele Rousseau, a mercenary member of the exploration team.
Carsten Norgaard as Rustin Quinn, a mercenary member of the exploration team.
Liz May Brice as Selene, the team's supervisor.
Glenn Conroy as Technician
Karima Adebibe as Sacrificial Maiden
Sam Troughton as Thomas "Tom" Parkes, a member of the exploration team.
Ian Whyte as The Predator, "Scar", one of three Predators who come to Earth to create and hunt Aliens within the pyramid as a rite of passage. Whyte played the lead Predator, called Scar in the film's credits due to the Predator marking himself with the Alien's acidic blood. Whyte also played the two Predators Chopper and Celtic.
Tom Woodruff, Jr. as The Alien, "Grid". The Alien played by Woodruff is listed in the film's credits as Grid, referencing crosshatch scars from Predator net constriction in the battle with Celtic.
Petr Jákl as Stone
Pavel Bezdek as Bass
Kieran Bew as Klaus
Carsten Voigt as Mikkel
Jan Filipensky as Boris
Adrian Bouchet as Sven
Eoin McCarthy as Karl
Andy Lucas as Juan Ramirez

tag: ul

text: Production[edit]

text: Fifth Alien film and sequel[edit]

text: Before 20th Century Fox gave Alien vs. Predator the greenlight, Aliens writer/director James Cameron had been working on a story for a fifth Alien film. Alien director Ridley Scott had talked with Cameron, stating "I think it would be a lot of fun, but the most important thing is to get the story right."[8] In a 2002 interview, Scott's concept for a story was "to go back to where the alien creatures were first found and explain how they were created"; this project eventually became Scott's film Prometheus (2012). On learning that Fox intended to pursue Alien vs. Predator, Cameron believed the film would "kill the validity of the franchise" and ceased work on his story, "To me, that was Frankenstein Meets Werewolf. It was Universal just taking their assets and starting to play them off against each other...Milking it."[9] After viewing Alien vs. Predator, however, Cameron remarked that "it was actually pretty good. I think of the five Alien films, I'd rate it third. I actually liked it. I actually liked it a lot."[9] Conversely, Ridley Scott had no interest in the Alien vs. Predator films. When asked in May 2012 if he had watched them, Scott laughed, "No. I couldn't do that. I couldn't quite take that step."[10] Director Neill Blomkamp would eventually go on to pitch his sequel to Aliens.[11]

text: Development[edit]

text: The concept of Alien vs. Predator originated from the Aliens versus Predator comic book in 1989, and was hinted at when an Alien skull appeared in a trophy case aboard the Predator ship in Predator 2.[12] Screenwriter Peter Briggs created the original spec screenplay in 1990–1991, which was based on the first comic series.[12] In 1991, he successfully pitched the concept to 20th Century Fox, who owned the film franchises, although the company did not move forward with the project until 2002. The project was delayed chiefly because the studio was working on Alien: Resurrection.[13] A draft penned by James DeMonaco and Kevin Fox was rejected by producer John Davis, who hoped to give the film an original approach by setting it on Earth.[14]

text: As there were six producers between the film franchises, John Davis had difficulty securing the rights as the producers were worried about a film featuring the two creatures. Paul W. S. Anderson pitched Davis a story he worked on for eight years, and showed him concept art created by Randy Bowen.[15] Impressed with Anderson's idea, Davis thought the story was like Jaws in that it "just drew you in, it drew you in".[16] Anderson started to work on the film after completing the script for Resident Evil: Apocalypse, with Shane Salerno (writer of Aliens vs. Predator: Requiem) co-writing. Salerno spent six months writing the shooting script, finished its development, and stayed on for revisions throughout the film's production.[17]

text: Story and setting[edit]

text: Early reports claimed the story was about humans who tried to lure Predators with Alien eggs, although the idea was scrapped.[18] Influenced by the work of Erich von Däniken, Anderson researched von Däniken's theories on how he believed early civilisations were able to construct massive pyramids with the help of aliens, an idea drawn from Aztec mythology.[19] Anderson wove these ideas into Alien vs. Predator, describing a scenario in which Predators taught ancient humans to build pyramids and used Earth for rite of passage rituals every 100 years in which they would hunt Aliens. To explain how these ancient civilisations "disappeared without a trace", Anderson came up with the idea that the Predators, if overwhelmed by the Aliens, would use their self-destruct weapons to kill everything in the area.[19] H. P. Lovecraft's novella At the Mountains of Madness (1931) served as an inspiration for the film, and several elements of the Aliens vs. Predator comic series were included.[15][20] Anderson's initial script called for five Predators to appear in the film, although the number was later reduced to three.[19]

text: As Alien vs. Predator is a sequel to the Predator films and prequel to the Alien series, Anderson was cautious of contradicting continuity in the franchises. He chose to set the film on the remote Norwegian Antarctic island of Bouvet commenting, "It's definitely the most hostile environment on Earth and probably the closest to an Alien surface you can get."[21] Anderson thought that setting the film in an urban environment like New York City would break continuity with the Alien series as the protagonist, Ellen Ripley, had no knowledge the creatures existed. "You can't have an Alien running around the city now, because it would've been written up and everyone will know about it. So there's nothing in this movie that contradicts anything that already exists."[21]

text: Casting[edit]

text: The first actor to be cast for Alien vs. Predator was Lance Henriksen, who played the character Bishop in Aliens and Alien 3. Although the Alien movies are set 150 years in the future, Anderson wanted to keep continuity with the series by including a familiar actor. Henriksen plays billionaire Charles Bishop Weyland, a character that ties in with the Weyland-Yutani Corporation. According to Anderson, Weyland becomes known for the discovery of the pyramid, and as a result the Weyland-Yutani Corporation models the Bishop android in the Alien films after him; "when the Bishop android is created in 150 years time, it's created with the face of the creator. It's kind of like Microsoft building an android in 100 years time that has the face of Bill Gates."[22]

text: Anderson opted for a European cast including Italian actor Raoul Bova, Ewen Bremner from Scotland, and English actor Colin Salmon. Producer Davis said, "There's a truly international flavor to the cast, and gives the film a lot of character."[23] Several hundred actresses attended the auditions to be cast as the film's heroine Alexa Woods. Sanaa Lathan was selected, and one week later she flew to Prague to begin filming. The filmmakers knew there would be comparisons to Alien heroine Ellen Ripley and did not want a clone of the character, but wanted to make her similar while adding something different.[23]

text: Anderson reported in an interview that California Governor Arnold Schwarzenegger was willing to reprise his role as Major Alan "Dutch" Schaeffer from Predator in a short cameo appearance if he lost the recall election on condition that the filming should take place at his residence.[24] Schwarzenegger, however, won the election with 48.58% of the votes and was unavailable to participate in Alien vs. Predator. Actress Sigourney Weaver, who starred as Ellen Ripley in the Alien series, said she was happy not to be in the film, as a possible crossover was "the reason I wanted my character to die in the first place", and thought the concept "sounded awful".[25][26]

text: Filming and set designs[edit]

text: Production began in late 2003 at Barrandov Studios in Prague, Czech Republic, where most of the filming took place. Production designer Richard Bridgland was in charge of sets, props and vehicles, based on early concept art Anderson had created to give a broad direction of how things would look. 25 to 30 life-sized sets were constructed at Barrandov Studios, many of which were interiors of the pyramid. The pyramid's carvings, sculptures, and hieroglyphs were influenced by Egyptian, Cambodian, and Aztec civilisations, while the regular shifting of the pyramid's rooms was meant to evoke a sense of claustrophobia similar to the original Alien film.[27] According to Anderson, if he was to build the sets in Los Angeles they would have cost $20 million. However, in Prague they cost $2 million, an important factor when the film's budget was less than $50 million.[15]

text: Third scale miniatures several meters in height were created to give the film the effect of realism, rather than relying on computer generated imagery (CGI). For the whaling station miniatures and life-sized sets, over 700 bags of artificial snow were used (roughly 15–20 tons).[16] A 4.5-meter miniature of an icebreaker with working lights and a mechanical moving radar was created, costing almost $37,000 and taking 10 weeks to create. Visual effects producer Arthur Windus, claimed miniatures were beneficial in the filming process: "With computer graphics, you need to spend a lot of time making it real. With a miniature, you shoot it and its there."[28] A scale 25-meter miniature of the whaling station was created in several months. It was designed so the model could be collapsed and then reconstructed, which proved beneficial for a six-second shot which required a re-shoot.[28]

text: Effects and creatures[edit]

text: Special effects company Amalgamated Dynamics Incorporated (ADI) was hired for the movie, having previously worked on Alien 3 and Alien: Resurrection. Visual special effects producers Arthur Windus and John Bruno were in charge of the project, which contained 400 effects shots.[28] ADI founders Alec Gillis, Tom Woodruff Jr., and members of their company, began designing costumes, miniatures and effects in June 2003. For five months the creatures were redesigned, the Predators wrist blades being extended roughly four times longer than those in the Predator films, and a larger mechanical plasma caster was created for the Scar Predator.[16]

text: The basic shape of the Predator mask was kept, although technical details were added and each Predator was given a unique mask to distinguish them from each other. These masks were created using clay, which was used to form moulds to create fiberglass copies. These copies were painted to give a weathered look, which Woodruff claims "is what the Predator is all about".[16] A hydraulic Alien puppet was created so ADI would be able to make movements faster and give the Alien a "slimline and skeletal" appearance, rather than using an actor in a suit. The puppet required six people to run it; one for the head and body, two for the arms, and a sixth to make sure the signals were reaching the computer. Movements were recorded in the computer so that puppeteers would be able to repeat moves that Anderson liked. The puppet was used in six shots, including the fight scene with the Predator which took one month to film.[16]

text: The crew tried to keep CGI use to a minimum, as Anderson said people in suits and puppets are scarier than CGI monsters as they are "there in the frame".[16] Roughly 70% of scenes were created using suits, puppets, and miniatures. The Alien queen was filmed using three variations: a 4.8-meter practical version, a 1.2-meter puppet, and a computer-generated version. The practical version required 12 puppeteers to operate,[15] and CGI tails were added to the Aliens and the queen as they were difficult to animate using puppetry.[23][29] The queen alien's inner-mouth was automated though, and was powered by a system of hydraulics. Anderson praised Alien director Ridley Scott's and Predator director John McTiernan's abilities at building suspense by not showing the creatures until late in the film, something Anderson wanted to accomplish with Alien vs. Predator. "Yes, we make you wait 45 minutes, but once it goes off, from there until the end of the movie, it's fucking relentless".[30]

text: Music[edit]

text: Austrian composer Harald Kloser was hired to create the film's score. After completing the score for The Day After Tomorrow, Kloser was chosen by Anderson as he is a fan of the franchises.[31] It was recorded in London, and was primarily orchestral as Anderson commented, "this is a terrifying movie and it needs a terrifying, classic movie score to go with it; at the same time it's got huge action so it needs that kind of proper orchestral support."[31]

text: The score was released on 31 August 2004, and received mixed reviews. James Christopher Monger of Allmusic thought Kloser introduced electronic elements well, and called "Alien vs. Predator Main Theme a particularly striking and serves as a continuous creative source for the composer to dip his baton in."[32] Mike Brennan of Soundtrack, however, said it "lacks the ingenuity of the previous trilogy and the Predator scores, which all shared a strong sense of rhythm in place of thematic content. Kloser throws in some interesting percussion cues ("Antarctica" and "Down the Tunnel"), but more as a sound effect than a consistent motif."[33] John Fallon of JoBlo.com compared it to character development in the film, "too generic to completely engage or leave a permanent impression."[34]

text: Reception[edit]

text: Box office[edit]

text: Alien vs. Predator was released in North America on 13 August 2004 in 3,395 theatres. The film grossed $38.2 million over its opening weekend for an average of $11,278 per theatre, and was number one at the box office. The film spent 16 weeks in cinemas and made $80,281,096 in North America.[35] It grossed $9 million in the United Kingdom, $16 million in Japan, and $8 million in Germany and totalled $92,262,423 at the international box office. This brought the film's worldwide gross to $172,543,519, making it the highest-grossing film in either the Predator or Alien franchises (excluding Prometheus, which grossed over $403 million worldwide[36]). It ranks second behind Aliens at the domestic box office, and fifth behind the first three Alien films and the first Predator, when adjusted for inflation.[37][38]

text: Critical response[edit]

text: The film was not screened in advance for critics. Alien vs. Predator received negative reviews.[39] On Rotten Tomatoes the film has a rating of 20%, based on 144 reviews, with the site's critical consensus reading, "Gore without scares and cardboard cut-out characters make this clash of the monsters a dull sit."[40] On Metacritic the film has a score of 29 out of 100, based on 21 critics, indicating "generally unfavorable reviews".[41] Audiences polled by CinemaScore gave the film an average grade of "B" on an A+ to F scale.[42]

text: Chief criticisms of the film included its dialogue, a PG-13 rating, the "fast-paced editing" during fight sequences, and lighting. However, special effects and set designs received praise.[40][41]

text: Rick Kisonak of Film Threat praised the film stating, "For a big dumb production about a movie monster smackdown, Alien vs. Predator is a surprisingly good time".[43] Ian Grey of the Orlando Weekly felt, "Anderson clearly relished making this wonderful, utterly silly film; his heart shows in every drip of slime."[43] Staci Layne Wilson of Horror.com called it "a pretty movie to look at with its grandiose sets and top notch creature FX, but it's a lot like Anderson's previous works in that it's all facade and no foundation."[41] Gary Dowell of The Dallas Morning News called the film, "a transparent attempt to jumpstart two run-down franchises".[43] Ed Halter of The Village Voice described the film's lighting for fight sequences as, "black-on-black-in-blackness",[44] while Ty Burr of The Boston Globe felt the lighting "left the audience in the dark".[45]

text: Home media releases[edit]

text: Alien vs. Predator was released on VHS and DVD in North America on 25 January 2005.[46] The DVD contained two audio commentaries. The first featured Paul W. S. Anderson, Lance Henriksen, and Sanaa Lathan, while the second included special effects supervisor John Bruno and ADI founders Alec Gillis and Tom Woodruff. A 25-minute "Making of" featurette and a Dark Horse AVP comic cover gallery were included in the special features along with three deleted scenes from the film. On release, Alien vs. Predator debuted at number 1 on the Top DVD Sales and Top Video Rental charts in North America.[47][48]

text: A two-disc "Extreme Edition" was released on 7 March 2005, featuring behind the scenes footage of the conception, pre-production, production, post-production, and licensing of the film. An "Unrated Edition" was released on 22 November 2005, containing the same special features as the Extreme Edition as well as an extra eight minutes of footage in the film. John J. Puccio of DVD Town remarked that the extra footage contained "a few more shots of blood, gore, guts, and slime to spice things up...and tiny bits of connecting matter to help us follow the story line better, but none of it amounts to much."[49] The film was released on Blu-ray Disc in North America on 23 January 2007.